A basic oxygen furnace (hereinafter "BOF") used to make steel includes an outer steel shell and a refractory lining inside the outer steel shell. Most basic oxygen furnaces are equipped with two lances, only one of which can be in an operative position above the furnace at a given time. One of the two lances is an idle side auxiliary lance that is kept on standby outside the perimeter of the furnace. The other lance is a main oxygen blowing refining lance which, during the steelmaking process, is located in the furnace above the bath. In conventional BOF shops, a motorized lance transport and elevator system is used to manipulate the main and auxiliary lances.
Due to the violent agitation of the melt during refining of the molten metal into steel, a material commonly known as skull, a mixture of molten metal and oxides, is deposited on the working surface of the furnace and on the lances. The formation of skull at the cone of the BOF is undesirable because it restricts the ability to lower lances and charge scrap into the cone of the furnace.
One way the problem of skulling at the furnace cone has been addressed is to use a lance dedicated to deskulling. Oxygen gas is blown from the deskulling lance to melt the skull at the furnace cone by moving the lance vertically up and down near the location of the skull.
Due to factors including wear, high temperature and the combustion of high velocity oxygen gas in the furnace, the refractory walls deteriorate and must be repaired or replaced. One way to maintain the refractory walls of the furnace is through a process known as slag splashing in which a lance is used to blow an inert gas toward the slag layer. This causes the slag to be splashed upwardly onto the refractory walls and to coat portions of the refractory walls that have been worn. The slag cools on the refractory walls, effectively repairing worn portions of the walls. However, the slag splashing process may increase the problem of skull build-up at the cone of the furnace.
In view of the problems of skulling at the cone of the furnace and deterioration of the refractory walls, some BOF shops employ an idle-side deskulling lance and a refining lance. The deskulling lance is used to melt the skull from the furnace cone and the refining lance is used for refining the molten metal and for the slag splashing operation. This selection of lances is undesirable. The slag splashing tends to coat the refining lance with skull which requires removing the lance from the furnace. Thus, the furnace must be shut down frequently to replace the skulled refining lance.
Other BOF shops employ one lance for refining the molten metal and another lance for the slag splashing operation. When the furnace cone must be deskulled, one of the lances must be replaced with a deskulling lance, which is undesirable in that it takes time to replace lances.